I was in charge of the whole design (like being my own client), with a team of scientists for research and advice, though I also did some research and learned everything they threw at me. On this illustration, the scientist mentors were Carolyn Tepolt (the Acidity scientist on the show), Kevin Miklaz, and Julia Stewart. The schedule only allowed me a few hours to understand the concepts.

This is just a selection of the studies produced, by far not all of them.

Unless noted otherwise, all quotes are my own, from the discussion with the scientists.

Acidity is the experiment I remember best from elementary and middle school science classes: how can anyone forget a strip of blank paper that suddenly takes on color! It’s magic! As I was finishing the Maillard Reaction illustration, Carolyn and Kevin got one step ahead with ideas of how this could be depicted: household items along a pH scale strip, also showing taste, and with the logarithmic aspect somewhere above it all. It sounded like a package ready to go!

When I heard logarithmic, the first thing I thought of was this film I saw a long time ago, created by fellow architects Ray & Charles Eames, entitled Powers of Ten. It’s the best experiential representation of just how big a 10x jump really is. So I gave it a try as a means to start. The “7” levels of the pH scale (without yet looking into it, I thought they increased proportionally from a central zero point, so 14/2 = 7) were one too many for a simple graphic. Either they didn’t fit or they decreased down to unnoticeable sizes. I based the colors on the old litmus paper test as a start.

The reactions to this were that, while it was an unusually interesting way of depicting the logarithmic scale, it ran backwards from convention (it would confuse scientists): the scale typically reads from left to right, 0 to 14! And there, I experienced my first professional cultural break: in science, conventions are important; in art and design, you typically try to break them. In this case, it just happened by chance as I was just putting things down to start.

“Here are some other thoughts. I missed that Carolyn said pickling above.

Is the link between acidity and sour taste correlated? I personally do not like tomato sauce/pasta dishes because it kind of “hurts” my stomach being so acidic, but it’s less sour than lemons… guess I don’t eat lemon juice either.

Is hot food acidic or something else?

I think ceviche would be a great example… it’s a big curiosity to understand how it “gets cooked.”

Would also be curious about the ripening level of fruits – how they go from sour to sweet, and thus change acidity levels? And how that relates to sugar… moving into how sugar ferments into alcohol… oh, no, it’s for high school students!

On the pH scale I think we should show foods… vinegar and baking soda, as I mentioned, are used in household cleaning.

When oil gets rancid, does it become acidic?

Relation to foul smell/deterioration and acidity?

Thanksgiving meal upset stomach… was it the wine?

What I would like to understand about acid is why it is a preservative. I guess because it kills the bacteria trying to flourish… It’s used in lotions, food, and a good example of it is in tabouleh (also jam, but that’s not a quick to make item). Tabouleh uses lemon juice.…In Romania, pickling (pickles, cabbage, green tomatoes, carrots) is done with salt and we always had the feeling that big brands in the US cheat (because it takes longer with salt) and put in vinegar, which doesn’t produce as good a taste, more soury than tasty… I think showing something about the bacteria living condition, what Kevin said about osmosis and cell walls breaking down. I also think it would be good to show that the sugar in something acidic (hot cocoa/milk) can overcome the sour taste and hide the fact that it’s acidic…“

Since the square example didn’t fit, I tried to do it with curves (above). Unfortunately, the same issue evolved…“I faked the curves because at 10x bigger with each jump the differences are extreme and the ‘curve’ just looks like a line following the ‘L’ edge of the poster… I feel that hockey [stick] line seems subtle… and the idea is of an explosion… That curve is approximate, but it doesn’t communicate to most people the big idea wise/big visual view that it’s a big change.”

The graph was still partly backwards, but it had to do with my free association: for some reason I felt that acidity must mean negativity (as if sweet things would be +, and sour things -) (refer to ion concentration several paragraphs lower). I guess science doesn’t go by feelings. “I thought bleach was acidic because it burns.” On this design I had less time to look everything up, since the Maillard Reaction had been so complicated.

Meanwhile, I was wondering what else one could show about this to make it a bit more interesting than just a graph. It didn’t seem as engaging as the other ones where you looked at what happens at molecular levels. I guess the challenge here was to depict the logarithm.

“Does acidity always have to involve water molecules disassociating hydrogens off of them?Do you always need this water element?I’m trying to think of what else to show besides the graph of food.”

As I added more items to the graph (including body fluids: stomach acid, saliva and blood, since they interact with the ingested food, we are familiar with them, and probably curious), I started playing with how the logarithmic scale is represented. “I put the squares back because as Julia mentioned, they make more of an impact than that skinny curve.”

Meanwhile, I wondered whether the exact pH numbers of the individual food items were important, or even correct. “I also am not sure about putting the numbers because they are the average off the internet… so not 100%.”

While adding more and more food items, I was amazed to discover that almost all foods are acidic: even potatoes, bananas, maple syrup, cheese, avocados, milk, and butter! “Been reading about how egg whites and egg yolks change pH levels due to travel, storage, and maybe in response to Salmonella… That’s the only basic food (except maybe also dates) that I’ve found, and of course baking power/baking soda.” In this light, the graph idea/layout was beginning to seem like it had something.

Since most foods are acidic, that is what we are better fit to taste. Kevin noted that our taste buds, when they detect sour, are actually measuring acidity, but that they are not equipped to detect basicity… it is just less tasty, bad, somehow, but hard to define, somewhat soapy and bitter. This gave me the idea of adding a tongue map. “I’m putting in more science info and possibly the tongue to show that taste exists for the sour stuff.” But after some research, I changed my mind. “I’m not showing the tongue because apparently the zoning of it is just a blown up “myth”… so much for my 8th grade science fair project…”

With development, the colors of the scale began to vary. Detailed pH scales and tests come in an array of colors; not just red to blue. The traditional litmus red-blue test only tells whether it’s an acid or a base, but is not very specific. “Looking for pH test kit colors, I see that in fact they often cover the whole rainbow, and it may be more appropriate to show it that way. Like the image of cabbage posted earlier. People might even be familiar if they use them for testing their soil or pool water…”

In all of these I was still assuming that 7, being neutral, represents a zero point of some sort (see how in all the graphs above the colored area starts big on one end, goes to a zero in the middle and then grows big again). Reading more about how the scale represents ion concentrations, it finally clicked that I had been drawing it wrong. The scale shows a continuous increase (or decrease) in + or – ion concentrations. The “zero” point in the middle is not “zero” at all, but a point at which the + and – ions are balanced or in the same amount: it’s more of a 1:1 point.

“BTW, I just realized I didn’t know what pH stands for and when I looked it up it said ‘potential Hydrogen’ which totally makes sense and so I’m going to add it!”

The pH name of the scale stands for “potential/power of Hydrogen” because the pH scale and test measure the amounts of Hydrogen ions (H+) [or Hydronium ions (H3O+) as the H+ tends to get attached to an H2O] in comparison with Hydroxide ions (HO-). You can see that in putting together an equal acid and base [H+ plus HO-], you get a neutral H2O, or water. What seems a little backwards to me is that while it is called potential/power of Hydrogen, as the numbers go up on the scale, the amount of Hydrogen ions actually decreases.

These two layouts (above and below) demonstrate a final understanding that the scale is about an exchange of +ions to -ions. On one side you have more of one, in the middle there are equal amounts of both, and at the other end there is more of the other.

The design below highlights the potential/power of Hydrogen idea, in that since you are measuring the amounts of Hydrogen +ions, those stand out as being more prominent (the red triangle). “I think the triangle in the middle works best because it frames the food and you can see more easily how many protons there are at that food level.” The areas (red and blue) are equal.

Between that and the final illustration, several changes occurred:

The graph took on curvature, to hint at the idea that it is not a 1:1 straight increase/decrease, but that it is logarithmic. As discussed earlier, because of the gigantic leaps between one number an the next, actual logarithmic change could not be shown.

Diagrams showing ion concentrations were added, since that is what the pH scale measures. To fit and balance the drawing, they were playfully moved around.

Hydronium (H3O+) ions replaced the Hydrogen (H+) ions, since in reality the H+ get attached to an H2O water molecule and become H3O+ ions, and that is what you measure.

I stuck with the original litmus test colors for: 1. clarity (in order for it to read well, the graph could only be of two color blocks); 2. because red is a prominent food color; and 3. because these colors weren’t yet featured in any of the other illustrations. I wanted the series of image colors, and geometries, to be of a wide variety, to make each experiment stand out as being unique.

Explanatory text was added. The numbers, plus names, identified the various objects, so that someone really curious can get up close and see. I put a note about the history of the scale, and wish now that I had also mentioned that the litmus test is 700 years old! In the definition of acidity, I tried to sneak in a pun! The quote for this illustration (Carolyn) tells something quite revealing that you aren’t consciously aware of: chemicals (materials) are constantly “changing/varying.”

The topic was stamped “material property,” as although the acidity test is a process, the term “acidity” refers to the property of a material, in this case a chemical property.